1. Technical Field
The present invention relates to an ink cartridge and a method for producing the ink cartridge, and more particularly to an ink cartridge comprising a molded article including a polypropylene-based resin polymerized by a gas-phase method and a method for producing the ink cartridge.
2. Related Art
A printer of a type utilizing a liquid ink for recording, particularly a printer of ink jet type, utilizes an ink cartridge as disclosed, for example, in References 1-3.
Such ink cartridges include one molded with a polypropylene-based (hereinafter simply referred to as PP) resin.
An ink cartridge molded from such polypropylene-based resin may have, for example, a form as shown in FIG. 1. The ink cartridge of the form shown in FIG. 1 is assembled by contacting a cartridge main body 15 and a cover member 13 as shown in FIG. 2, and applying a pressure and a vibration thereby executing a vibration-welding.
The polypropylene-based resin employed for molding the cartridge main body 15 and the cover member 13, of such ink cartridge is prepared in the following manner.
At first, in a hydrocarbon solvent, propylene gas is injected in the presence of a metal chloride catalyst and under heating and pressurizing to synthesize PP by polymerization, thereby obtaining PP powder. This process is called a solvent method. The obtained PP powder may be inconvenient for handling because of its form, and contains free chlorine ions which are derived from the metal chloride catalyst and which may affect a service life and the like of the molded article. For avoiding these drawbacks, the PP powder is mixed with a chlorine ion neutralizer formed by a fatty acid metal salt and processed in a pelletizer to obtain PP pellets including reduced free chlorine ions and having an appropriate particle size.
The cartridge main body 15 and the cover member 13 have been molded from such PP pellets.
However, the solvent method for producing the polypropylene-based resin has been associated with limitations of a high cost of raw materials and of requiring complex and large facilities.
These drawbacks have been solved by a suitable metal chloride catalyst which has been found later and has enabled the polymerization-production of polypropylene-based resin by a gas-phase method. The neutralization of free chlorine ions derived from the catalyst and the palletizing are conducted in the same manner as in the solvent method.
The polymerization-production of polypropylene-based resin by the gas-phase method is lower in the cost of the raw materials and allows to use simpler and smaller facilities, in comparison with the solvent method.
The neutralization of free chlorine ions derived from the catalyst and the palletizing are same as in the solvent method.
Reference 1: JP-A-5-270001
Reference 2: JP-A-7-125238
Reference 3: JP-A-10-16249
However, an assembling of an ink cartridge by vibration-welding, tried with a cartridge main body 15 and a cover member 13 molded with a polypropylene-based resin polymerized by the gas-phase method, has resulted in a drawback that mutually contacting portions (director portions) thereof are broken and a satisfactory welding has not been attained.
Also when an ink is contained in a container utilizing such PP, including that obtained by the prior solvent method, and is maintained in a harsh environment (high temperature or low temperature) for a prolonged period (for example, about 50 hours or longer at about 60° C. or about 5° C.), the ink shows a drawback of generating a foreign substance therein.